Electrical circuit (e.g., chip, die or integrated circuit, etc.) is one of the most essential hardware foundations of modern information society; different electrical circuits can be connected into an interconnection system by channel(s), so these electrical circuits can exchange signals (e.g., information, data, messages, commands and/or packages) to coordinate and cooperate with each other for implementing integrated macro functions. However, characteristics of channel will impact quality of signal exchange. Generally, channel is of low-pass nature, and therefore will suppress high-frequency portion of signal and cause signal distortion; for example, when an electrical circuit acts as a transmitter and transmits a signal of a square waveform to another electrical circuit which acts as a receiver, the receiver will receive a slowly rising and falling waveform, instead of a square waveform with sharp rising and falling edges. In the waveform received by the receiver, the slowly rising portion is referred to as a pre-cursor, the peak of slowly rising forms a main cursor, and the slowly falling portion after the peak is referred to as a post-cursor. Signal distortion will cause ISI (inter-symbol interference) and degrade quality of signal transmission, e.g., increase bit error rate.
To compensate impact of channel, transmitter and receiver are respectively equipped with filtering and equalization mechanisms. For example, the filtering mechanism of transmitter can include a FIR (finite impulse response) filter for de-emphasis; the equalization mechanism of receiver can include a CTLE (continuous time linear equalizer) and a DFE (decision feedback equalizer). When a transmitter intends to send a signal to a receiver, filter of the transmitter will filter the outgoing signal based on a plurality of filter taps, so the filtered signal can be driven to a channel; when the receiver receives the incoming signal from the channel, the receiver will equalize the received signal based on a plurality of equalizer taps, and then retrieve contents and/or other information (e.g., clock) from the equalized signal.
Filter taps of the transmitter filter define characteristics of filtering; to effectively compensate channel effect, filter taps need to actually reflect channel characteristics, e.g., pre-cursor and post-cursor due to channel. However, known prior art fails to fully consider complete channel characteristics when setting and tuning filter taps of transmitter filter.